Evaluation of the correlation between fetuin-B levels and essential hypertension: a cross-sectional study

Background

Fetuin-B, a cytokine that regulates lipid metabolism, has recently been linked to cardiovascular diseases such as coronary heart disease. In this study, we discussed the relationship between fetuin-B and essential hypertension.

Method

A bioinformatics analysis of fetuin-B was performed. A total of 206 with essential hypertension and 180 age- and-sex-matched healthy subjects were enrolled. Plasma fetuin-B, endothelin 1 (ET-1), nitric oxide (NO), and adiponectin (ADI) levels were measured using ELISA kits.

Results

Bioinformatics analysis has revealed that fetuin-B plays an important role in pathways such as lipid metabolism. Compared with healthy subjects, serum fetuin-B levels in patients with essential hypertension were significantly increased. Correlation analysis showed that the serum fetuin-B level was positively correlated with systolic blood pressure (SBP), diastolic blood pressure, body mass index, fat percentage in vivo, waist-hip ratio, intima-media thickness, low-density lipoprotein cholesterol (LDL-C), glutamyltranspeptidase, alanine transaminase, albumin, fasting blood glucose (FBG), glycated hemoglobin, and ET-1 in the overall study subjects (all P < 0.05) and negatively correlated with HDL-C, ADI, and NO (all P < 0.05). Multivariate linear regression analysis showed that SBP, FBG, LDL-C, ADI, and ET-1 were independent factors affecting serum fetuin-B. A binary logistic regression analysis showed that fetuin-B was an independent risk factor for primary hypertension (odds ratio: 1.060, 95% CI: 1.034-1.086, P < 0.001). Receiver operating characteristic curve analysis was used to evaluate the predictive value of fetuin-B for primary hypertension, and the optimal cutoff point was 83.14 μg/mL (sensitivity 77.4%, specificity 63.3%) (area under the curve) = 0.7738, 95% CI 0.7276-0.8200, P < 0.001).

Conclusion

Elevated fetuin-B levels are associated with an increased risk of essential hypertension.

Hepatokines fetuin A and fetuin B status in women with/without gestational diabetes mellitus

OBJECTIVES

To assess circulating fetuin A and fetuin B levels in participants with and without Gestational Diabetes Mellitus (GDM) and to find out their correlations with other different parameters relating to gestational diabetes in Saudi women.

METHODS

A total of 123 Saudi pregnant women (N: 46 GDM and N: 77 healthy control) were included in this observational study. Fasting blood samples were collected to assess serum lipids, insulin and fetuin A and fetuin B. Serum fetuin A and fetuin B were quantified by commercially available kits.

RESULTS

The median value of fetuin A was slight lower in GDM patients [2003 pg/ml (866-3369)] than in the control group [2015 pg/ml (1060-2951)] without significant difference (P=0.95). The median value of fetuin B was also slight lower in GDM patients [3292 ng/ml (782-6740)] than the control group [3514 ng/ml (364-14854)] but without significant difference (P=0.564). There was a significant inverse correlation between fetuin B and total cholesterol in control group.

CONCLUSIONS

The present study did not find a significant association between fetuins A and B with GDM or insulin resistance, but there was a significant inverse correlation between fetuin B and total cholesterol in the control group, reflecting good glucose control and adequate use of lipids in the nutrition of the fetus. Further research is required in the future to understand fetuin's role in the progression of GDM in Saudi women.

Predıctıve value of pregnancy of follıcular fluıd fetuın-A and -B levels ın infertıle women after intra-cytoplasmic sperm injection

AIM

We aimed to investigate the value of follicular fluid fetuins-A and -B to predict successful IVF and pregnancy outcomes in infertile women with poor, normal, and high ovarian reserve.

METHODS

The follicular fluid of 96 infertile women who underwent intra-cytoplasmic sperm injection (ICSI) procedure was analyzed. Fetuins-A and -B levels were examined and compared in those who could achieve pregnancy and those who could not. Receiver operating characteristic curve analyzes were used to determine cut-off and statistically significant associations for fetuins-A and -B.

RESULTS

Follicular fluid fetuin-A levels were higher in cases with weak ovarian reserve (OR) (p < 0.05) and higher in patients who did not achieve clinical pregnancy (p < 0.05). Conversely, the follicular fluid fetuin-B levels were lower in cases with poor OR (p < 0.05) and were lower in patients who did not achieve a clinical pregnancy (p < 0.05). A follicular fluid fetuin-A concentration ≤ 19.12 ng/mL had a sensitivity and specificity of 94.74% and 93.1%, respectively, at predicting clinical pregnancy. While the follicular fluid fetuin-B concentration >24.7 ng/mL had sensitivity and specificity of 71.1% and 51.7%, respectively, for clinical pregnancy prediction.

CONCLUSION

Overall, high levels of follicular fluid fetuin-A may be independently associated with unsuccessful IVF irrespective of OR grouping. A low level of follicular fetuin-B was also associated with failed IVF. The sensitivity and specificity were found to be higher for fetuin-A in predicting clinical pregnancy. Therefore, the follicular fluid fetuin-A may be more predictive for successful IVF and clinical pregnancy outcomes than follicular fluid fetuin-B.

High Fat, High Sugar Diet and DJOS Bariatric Surgery Influence Plasma Levels of Fetuin-B, Growth Differentiation Factor-15, and Pentraxin 3 in Diet-Induced Obese Sprague-Dawley Rats

The liver plays a central role in glucose and fatty acid metabolism and acts as an endocrine organ that secretes hepatokines with diverse systemic effects. The study aimed to examine the influence of duodenojejunal omega switch (DJOS) bariatric surgery in combination with different diets on glucose administration parameters and hepatokines levels. After 8 weeks on high fat, high sugar diet (HFS) or control diets (CD), Sprague-Dawley rats underwent DJOS or SHAM (control) surgery. For the next 8 weeks after the surgery, half of DJOS and SHAM-operated animals were kept on the same diet as before, and half had a diet change. The oral glucose tolerance test (OGTT) was performed three times: 8 weeks before and 4 and 8 weeks after surgery. Fetuin-B, growth differentiation factor-15 (GDF-15), pentraxin 3 (PTX3) plasma levels were analyzed. DJOS surgery had a beneficial effect on oral glucose tolerance test (OGTT) results and the area under the curve (AUC_OGTT). The OGTT results depended on the time elapsed after the surgery, the type of diet used, the surgery performed, and the interaction between these factors. DJOS bariatric surgery reduced fetuin-B and GDF15 plasma levels. Interaction between the type of surgery performed and diet used influenced the fetuin-B and PTX-3 plasma levels. A dietary regime is essential to achieve therapeutic and clinical goals after bariatric surgery.

Association of serum fetuin-B with insulin resistance and pre-diabetes in young Chinese women: evidence from a cross-sectional study and effect of liraglutide

Background and Aims

Fetuin-B has been reported to be involved in glucose and lipid metabolism and associated with the occurrence of diabetes. The main purpose of this study is to explore the changes of circulating fetuin-B in young women with pre-diabetes and to analyze the relationship between fetuin-B and the occurrence and development of IR.

Methods

A total of 304 women were enrolled in this study and subjected to both OGTT and EHC. A subgroup of 26 overweight/obese womenwas treated with Lira for 24 weeks. serum fetuin-B concentrations were measured by ELISA.

Results

In IGT and IR-NG groups, serum fetuin-B levels were higher than those in the NGT group. The serum fetuin-B levels in the IGT group were higher than those in the IR-NG group. serum fetuin-B was positively correlated with BMI, WHR, 2h-BG, FIns, HbA1c, and HOMA2-IR, but negatively correlated with the M-value in all study populations. Multiple stepwise regression analysis showed that the M-value was independently and inversely associated with serum fetuin-B. Logistic regression analysis showed that serum fetuin-B was independently associated with IGT and significantly increased the risk of IGT. During the OGTT, serum fetuin-B increased significantly in the NGT group, but there were no significant changes in other groups. During the EHC, serum fetuin-B increased in the IGT group, but there was no change in other groups. After Lira intervention, serum fetuin-B decreased significantly in IGT women.

Conclusions

serum fetuin-B levels are elevated in young women with IR or IGT and may be associated with IR.

Limited proteolysis by acrosin affects sperm-binding and mechanical resilience of the mouse zona pellucida

The encounter of oocyte and sperm is the key event initiating embryonic development in mammals. Crucial functions of this existential interaction are determined by proteolytic enzymes, such as acrosin, carried in the sperm head acrosome, and ovastacin, stored in the oocyte cortical granules. Ovastacin is released upon fertilisation to cleave the zona pellucida, a glycoprotein matrix surrounding the oocyte. This limited proteolysis hardens the oocyte envelope, and thereby provides a definitive block against polyspermy and protects the developing embryo. On the other hand, acrosin, the renowned and most abundant acrosomal protease, has been thought to enable sperm to penetrate the oocyte envelope. Depending on the species, proteolytic cleavage of the zona pellucida by acrosin is either essential or conducive for fertilisation. However, the specific target cleavage sites and the resulting physiological consequences of this proteolysis remained obscure. Here, we treated native mouse zonae pellucidae with active acrosin and identified two cleavage sites in zona pellucida protein 1 (ZP1), five in ZP2 and one in ZP3 by mass spectrometry. Several of these sites are highly conserved in mammals. Remarkably, limited proteolysis by acrosin leads to zona pellucida remodelling rather than degradation. Thus, acrosin affects both sperm binding and mechanical resilience of the zona pellucida, as assessed by microscopy and nanoindentation measurements, respectively. Furthermore, we ascertained potential regulatory effects of acrosin, via activation of latent pro-ovastacin and inactivation of fetuin-B, a tight binding inhibitor of ovastacin. These results offer novel insights into the complex proteolytic network modifying the extracellular matrix of the mouse oocyte, which might apply also to other species.

Acute Hyperenergetic, High-Fat Feeding Increases Circulating FGF21, LECT2, and Fetuin-A in Healthy Men

BACKGROUND

Hepatokines such as fibroblast growth factor 21 (FGF21), leukocyte cell-derived chemotaxin 2 (LECT2), fetuin-A, fetuin-B, and selenoprotein P (SeP) are liver-derived proteins that are modulated by chronic energy status and metabolic disease. Emerging data from rodent and cell models indicate that hepatokines may be sensitive to acute nutritional manipulation; however, data in humans are lacking.

OBJECTIVE

The aim was to investigate the influence of hyperenergetic, high-fat feeding on circulating hepatokine concentrations, including the time course of responses.

METHODS

In a randomized, crossover design, 12 healthy men [mean ± SD: age, 24 ± 4 y; BMI (kg/m2), 24.1 ± 1.5] consumed a 7-d hyperenergetic, high-fat diet [HE-HFD; +50% energy, 65% total energy as fat (32% saturated, 26% monounsaturated, 8% polyunsaturated)] and control diet (36% total energy as fat), separated by 3 wk. Whole-body insulin sensitivity was assessed before and after each diet using oral-glucose-tolerance tests. Fasting plasma concentrations of FGF21 (primary outcome), LECT2, fetuin-A, fetuin-B, SeP, and related metabolites were measured after 1, 3, and 7 d of each diet. Hepatokine responses were analyzed using 2-factor repeated-measures ANOVA and subsequent pairwise comparisons.

RESULTS

Compared with the control, the HE-HFD increased circulating FGF21 at 1 d (105%) and 3 d (121%; P ≤ 0.040), LECT2 at 3 d (17%) and 7 d (32%; P ≤ 0.004), and fetuin-A at 7 d (7%; P = 0.028). Plasma fetuin-B and SeP did not respond to the HE-HFD. Whole-body insulin sensitivity was reduced after the HE-HFD by 31% (P = 0.021).

CONCLUSIONS

Acute high-fat overfeeding augments circulating concentrations of FGF21, LECT2, and fetuin-A in healthy men. Notably, the time course of response varies between proteins and is transient for FGF21. These findings provide further insight into the nutritional regulation of hepatokines in humans and their interaction with metabolic homeostasis. This study was registered at clinicaltrials.gov as NCT03369145.

Fetuin-A and Fetuin-B in Non-Alcoholic Fatty Liver Disease: A Meta-Analysis and Meta-Regression

The magnitude of the effect of fetuin-A and fetuin-B on non-alcoholic fatty liver disease (NAFLD) remains undefined. Therefore, the aim of this study was to synthesize previous findings to obtain a reliable estimation of this relationship. This study was registered in PROSPERO with the number CRD42019126314. Studies published not later than March 2019, examining the relationship between fetuin-A, fetuin-B, and NAFLD, were identified by a systematic search in the electronic databases of the Web of Science, PubMed, Embase, and Cochrane Library. Pooled estimates of standardized mean difference (SMD), calculated using the random-effects model in a meta-analysis, were applied to estimate the strength of the association between fetuin-A, fetuin-B, and NAFLD. Thirty publications were identified and analyzed based on specified inclusion criteria. Collectively, they consisted of 3800 NAFLD participants and 3614 controls. Compared with the controls, significant higher values of the fetuin-A (SMD = 0.83, 95% CI: 0.59 to 1.07, Z = 6.82, p < 0.001) and fetuin-B (SMD = 0.18, 95% CI: 0.02 to 0.33, Z = 2.27, p = 0.023) were observed in NAFLD patients. Meanwhile, in the subgroup analysis, the effect value of fetuin-A in the NASH group was significantly higher than that in the NAFL group (p = 0.036). The findings of this study suggest that elevated fetuin-A and fetuin-B may independently indicate the occurrence of NAFLD. Nevertheless, further research is needed to confirm these results.

Increased serum fetuin-B concentration is associated with HOMA-β and indices of liver steatosis in women with polycystic ovary syndrome: a pilot study

OBJECTIVE

PCOS women are characterized by insulin resistance and have higher tendency to the development of hepatic steatosis. Fetuin-B has been introduced as a hepatokine/adipokine, which is increased in hepatic steatosis and may be connected with glucose metabolism disturbances. The aim of the study was to evaluate the relationships between serum fetuin-B concentration and indices of insulin resistance, insulin secretion and markers of liver steatosis in PCOS women in comparison to the control group.

PATIENTS AND METHODS

The study group included 108 women - 57 women with PCOS and 51 women matched for age and BMI as a control group. Serum concentration of fetuin-B was estimated. Homeostasis model assessment of insulin resistance (HOMA-IR) and homeostasis model assessment β cell function (HOMA-β) were calculated. Fatty liver index (FLI), lipid accumulation product (LAP) and visceral adiposity index (VAI) were used as markers of liver steatosis.

RESULTS

We found higher serum concentration of fetuin-B and FLI in PCOS women in comparison to the control group (all P < 0.05). We observed a positive relationship between serum fetuin-B concentration and HOMA-β (r = 0.43, P = 0.01), HOMA-IR (r = 0.31, P = 0.01), FLI (r = 0.29, P = 0.02), VAI (r = 0.29, P = 0.02) and LAP (r = 0.32, P = 0.01) in PCOS women. We also noticed a relationship between HOMA-IR and FLI (r = 0.42, P = 0.01), VAI (r = 0.38, P = 0.004) and LAP (r = 0.41, P = 0.001) in this group. Multiple regression analysis revealed that HOMA-β (β = 0.39, P = 0.002) and LAP (β = 0.27, P = 0.02) were independently connected with serum fetuin-B levels in women with PCOS.

CONCLUSIONS

Serum fetuin-B levels are higher in women with PCOS and are independently connected with HOMA-β and hepatic steatosis.

Serum fetuin-B is positively associated with intrahepatic triglyceride content and increases the risk of insulin resistance in obese Chinese adults: A cross-sectional study

BACKGROUND

Fetuin-B impairs insulin action in myotubes and hepatocytes and causes glucose intolerance in mice. This study explored the correlation between serum fetuin-B and intrahepatic triglyceride (IHTG) content, and the association between fetuin-B and the risk of insulin resistance in the general adult population.

METHODS

A cross-sectional study of 1318 obese adults who underwent serum fetuin-B testing and hepatic ultrasonography was conducted in Xiamen, China. The IHTG content was determined in 428 subjects by magnetic resonance spectroscopy.

RESULTS

Non-alcoholic fatty liver disease prevalence was significantly higher in those with the highest serum fetuin-B concentrations and the highest IHTC content (Tertile 3) than in subjects in Tertiles 1 and 2 (62.6% vs 60.7% and 54.3%, respectively [P = 0.032], and 15.3% vs 12.8% and 12.7%, respectively [P = 0.049]). There was a significant association between increasing serum fetuin-B tertiles and both increasing fasting insulin concentrations (mean [± SD] 11.9 ± 6.8, 12.7 ± 7.6, and 13.3 ± 6.4 mIU/L in Tertiles 1, 2 and 3, respectively; P = 0.006) and prevalence of insulin resistance (54.4%, 58.9%, and 64.5% in Tertiles 1, 2 and 3, respectively; P = 0.010). In linear regression analysis, IHTG content was independently and positively correlated with serum fetuin-B (regression coefficient 0.015; P = 0.045). With adjustment for potential confounders, serum fetuin-B was independently associated with increased risk of insulin resistance, with an adjusted odds ratio per standard deviation increase in fetuin-B of 1.14 (95% confidence interval 1.01-1.30; P = 0.031).

CONCLUSIONS

The results demonstrate the role of fetuin-B linking liver fat accumulation to insulin resistance in humans.

Intracellular activation of ovastacin mediates pre-fertilization hardening of the zona pellucida

STUDY QUESTION

How and where is pro-ovastacin activated and how does active ovastacin regulate zona pellucida hardening (ZPH) and successful fertilization?

STUDY FINDING

Ovastacin is partially active before exocytosis and pre-hardens the zona pellucida (ZP) before fertilization.

WHAT IS KNOWN ALREADY

The metalloproteinase ovastacin is stored in cortical granules, it cleaves zona pellucida protein 2 (ZP2) upon fertilization and thereby destroys the ZP sperm ligand and triggers ZPH. Female mice deficient in the extracellular circulating ovastacin-inhibitor fetuin-B are infertile due to pre-mature ZPH.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

We isolated oocytes from wild-type and ovastacin-deficient (Astlnull) FVB mice before and after fertilization (in vitro and in vivo) and quantified ovastacin activity and cleavage of ZP2 by immunoblot. We assessed ZPH by measuring ZP digestion time using α-chymotrypsin and by determining ZP2 cleavage. We determined cellular distribution of ovastacin by immunofluorescence using domain-specific ovastacin antibodies. Experiments were performed at least in triplicate with a minimum of 20 oocytes. Data were pre-analyzed using Shapiro-Wilk test. In case of normal distribution, significance was determined via two-sided Student's t-test, whereas in case of non-normal distribution via Mann-Whitney U-test.

MAIN RESULTS AND THE ROLE OF CHANCE

Metaphase II (MII) oocytes contained both inactive pro-ovastacin and activated ovastacin. Immunoblot and ZP digestion assays revealed a partial cleavage of ZP2 even before fertilization in wild-type mice. Partial cleavage coincided with germinal-vesicle breakdown and MII, despite the presence of fetuin-B protein, an endogenous ovastacin inhibitor, in the follicular and oviductal fluid. Upon exocytosis, part of the C-terminal domain of ovastacin remained attached to the plasmalemma, while the N-terminal active ovastacin domain was secreted. This finding may resolve previously conflicting data showing that ovastacin acts both as an oolemmal receptor termed SAS1B (sperm acrosomal SLLP1 binding protein; SLLP, sperm lysozyme like protein) and a secreted protease mediating ZP2 cleavage.

LIMITATIONS, REASONS FOR CAUTION

For this study, only oocytes isolated from wild-type and ovastacin-deficient FVB mice were investigated. Some experiments involved oocyte activation by the Ca2+ ionophore A23187 to trigger ZPH.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides a detailed spatial and temporal view of pre-mature cleavage of ZP2 by ovastacin, which is known to adversely affect IVF rate in mice and humans.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was supported by the Center of Natural Sciences and Medicine and by a start-up grant of the Johannes Gutenberg University Mainz to W.S., and by a grant from Deutsche Forschungsgemeinschaft and by the START program of the Medical Faculty of RWTH Aachen University to J.F. and W.J.D. There are no competing interests to declare.

The hepatokines fetuin-A and fetuin-B are upregulated in the state of hepatic steatosis and may differently impact on glucose homeostasis in humans

The liver is a central regulator of whole body glucose, and lipid homeostasis and hepatokines, like fetuin-A, have been identified as markers and mediators of fatty liver-induced cardiometabolic risk. The closely related protein fetuin-B was shown to be upregulated in the fatty liver and to impact on glucose homeostasis in mice. In the present study we aimed to test the relevance of these findings in humans. In 55 subjects, hepatic mRNA expression of both hepatokines, fetuin-A and fetuin-B, associated positively with liver triglyceride content, whereas only fetuin-A expression associated with the homeostatic model assessment of insulin resistance. In 220 subjects who underwent precise metabolic phenotyping, circulating fetuin-A, but not fetuin-B, associated positively with liver fat content, and negatively with insulin sensitivity, measured during the oral glucose tolerance test (OGTT) and during the euglycemic, hyperinsulinemic clamp. Both circulating fetuin-A and fetuin-B correlated positively with the glucose area under the curve during the OGTT, but after additional adjustment for insulin sensitivity this relationship remained significant only for fetuin-B. In conclusion, despite the fact that the two hepatokines, fetuin-A and fetuin-B, are upregulated in the state of hepatic steatosis in humans, it appears that they differently impact on glucose homeostasis. Our data are in agreement with observations that fetuin-A can alter insulin signaling and that fetuin-B may regulate glucose homeostasis via so far unknown effects, possibly on glucose effectiveness.

Down-regulation of the liver-derived plasma protein fetuin-B mediates reversible female infertility

STUDY QUESTION

Does antisense oligonucleotide (ASO)-mediated down-regulation of serum fetuin-B cause infertility like fetuin-B gene deficiency in female mice?

SUMMARY ANSWER

Pharmacological fetuin-B down-regulation by ASO therapy results in reversible infertility in female mice.

WHAT IS KNOWN ALREADY

Female fetuin-B deficient (Fetub^-/-) mice are infertile owing to premature zona pellucida (ZP) hardening. Enzyme activity studies demonstrated that fetuin-B is a potent and highly specific inhibitor of the zona proteinase ovastacin, which cleaves ZP protein 2 (ZP2) and thus mediates definitive ZP hardening.

STUDY DESIGN, SIZE, DURATION

Ten fetuin-B ASO boli (100 mg/kg) were injected s.c. over 20 days in 12 female mice, and 10 phosphate-buffered saline (PBS)-treated mice were used as control. At day 20 females were mated to evaluate fetuin-B as a potential molecular target for contraception. ASO and PBS treatment was continued for ten injections. After treatment cessation at day 50, mating was continued to investigate if infertility was reversible.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We generated fetuin-B/ovastacin double deficient (Fetub^-/-, Astl^-/-) mice by conventional breeding to test if fertility of Fetub^-/- female mice was restored when the target proteinase would likewise be deleted. At least five matings with each female genotype (Fetub^-/- single deficient, Astl^-/- single deficient, Fetub^-/-, Astl^-/- double deficient) were performed. To test the contraceptive effect of fetuin-B down-regulation, 22 female mice (6-13 weeks old) were treated with repetitive boli of 100 mg/kg fetuin-B ASO (n = 12) or PBS (n = 10) and mated continuously. Serum fetuin-B was determined by immunoblot before, during and after the ASO treatment. After 3 weeks of ASO treatment, in 6 females Fetub mRNA in liver was analyzed by PCR, and six PBS-treated females were used as control. Aspartate (AST) and alanine aminotransferase (ALT) were also measured in serum of six mice in each group. To determine the minimum permissive serum fetuin-B concentration required for successful fertilization IVF was performed in five fetuin-B ASO-treated mice. As a control, six females were injected with control oligonucleotides and six females were left untreated.

MAIN RESULTS AND THE ROLE OF CHANCE

Fertility of Fetub^-/- female mice was restored by additional ovastacin deficiency (Astl^-/-). Unlike Fetub^-/- mice, female Fetub^-/-, Astl^-/- mice were fertile, confirming ovastacin as a primary molecular target of fetuin-B. At day 20, after receiving 10 fetuin-B ASO boli, serum fetuin-B was down-regulated to 8 ± 6% (mean ± SD) of baseline level. Fetuin-B down-regulation was confirmed at the mRNA level. Fetuin-B ASO-treated females had 12.1 ± 3.1% of the liver Fetub mRNA level seen in PBS-treated females. In the following mating study, 11 out of 12 mated females failed to become pregnant during 50 days of ASO treatment and continuous mating from day 20 onwards. IVF of oocytes derived from ASO-treated females suggested that a serum fetuin-B level of less than 10 µg/ml was required to prevent pregnancy. Withdrawal of ASO treatment normalized serum fetuin-B and restored fertility; all female mice became pregnant and had litters within 60.3 ± 35.9 days after cessation of ASO treatment. The first litter was significantly smaller than that of control mice (4.6 ± 2.3 versus 6.7 ± 1.8 pups, n = 20, P = 0.04) but the smaller litter size was only temporary. The size of the second litter was similar to the first litter of control mice (7.6 ± 1.3 versus 6.7 ± 1.8 pups, n = 18, P = 0.25).

LIMITATIONS, REASONS FOR CAUTION

The repeated dose of 100 mg/kg fetuin-B ASO boli caused an increased serum ALT and AST activity, suggesting hepatotoxicity. Daily vaginal plug checks indicated successful mating, but mating plugs in ASO-treated mice were less stable (vaginal tract not closed) than in control mice.

WIDER IMPLICATIONS OF THE FINDINGS

Pharmacological fetuin-B down-regulation in mice caused reversible infertility. Control of ovastacin proteinase activity by fetuin-B is a necessary determinant of female fertility that can serve as a target for female contraception. Although promising in terms of human contraception, further studies analyzing the balance between sufficient fetuin-B down-regulation and tolerable side effects are required to improve safety before transfer into human reproductive biology can be considered.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTERESTS

The research was supported by a grant from Deutsche Forschungsgemeinschaft and by the START program of the Medical Faculty of RWTH Aachen University. The authors E.D., J.F. and W.J.-D. are named inventors on a patent application of RWTH Aachen University covering the use of fetuin-B in ovary and oocyte culture. No conflict of interest is declared by C.S. and A.C.

Association of high fetuin-B concentrations in serum with fertilization rate in IVF: a cross-sectional pilot study

STUDY QUESTION

Is serum fetuin-B associated with the fertilization rate in in vitro fertilization (IVF)?

SUMMARY ANSWER

Serum fetuin-B increased during IVF cycles when oocytes could be fertilized while remained unchanged in fertilization failure.

WHAT IS KNOWN ALREADY

Fetuin-B deficiency in mice causes premature zona pellucida hardening mediated by the zona protease ovastacin. Thus fetuin-B deficiency renders females infertile.

STUDY DESIGN, SIZE, DURATION

We determined the human serum fetuin-B reference range, studying longitudinally, over the course of one month, five male and seven female volunteers without hormone treatment and four female volunteers on varying hormonal contraception. We sampled blood and determined serum fetuin-B, luteinizing hormone (LH), estradiol (E2) and progesterone (P4). In addition, we determined serum fetuin-B and estradiol in eight women undergoing intracytoplasmatic sperm injection (ICSI, nine ICSI cycles) and 19 women undergoing IVF (21 IVF cycles) after ovarian stimulation with recombinant human follicular stimulating hormone (rFSH) and/or a combined medication of FSH and LH. At least three blood samples were analyzed in each cycle. We compared serum fetuin-B and follicular fluid fetuin-B in nine patients by measuring follicular fetuin-B in pooled follicular fluid, and in fluid obtained from individual follicles. Samples were drawn from January 2012 to March 2014.

PARTICIPANTS/MATERIALS, SETTING, METHOD

All volunteers and patients gave informed consent. Fetuin-B was measured employing a commercial sandwich enzyme-linked immunosorbent assay. Serum fetuin-B was determined as duplicates in 5 male (34 ± 14.6 years) and 11 female volunteers (29.4 ± 4.1 years) as well as in female volunteers on hormonal contraception (30.0 ± 6.5 years). The duplicate standard deviation was 4.0 ± 2.3%. The contraceptive drugs were mono or combined preparations containing 0-0.03 mg ethinyl estradiol, and 0.15-3.0 mg of various progestins. In addition, serum fetuin-B was determined as triplicates in 27 female patients undergoing conventional IVF (19) or ICSI (8). The triplicate standard deviation was 3.3 ± 1.8%. IVF was declared as 'successful', if at least one oocyte was fertilized, and 'unsuccessful', if no oocyte could be fertilized. Patient age was 34.4 ± 4.4 years in successful IVF, and 35.4 ± 3.3 years in unsuccessful IVF. Serum and follicular fluid of patients undergoing controlled ovarian hyperstimulation were analyzed. Serum was drawn at the day of follicle aspiration.

MAIN RESULTS AND THE ROLE OF CHANCE

Serum fetuin-B and follicular fluid fetuin-B were not significantly different in six out of nine patients suggesting, in principle, free exchange of fetuin-B between serum and follicular fluid. Thus serum fetuin-B may be used as a proxy of follicular fluid fetuin-B. Serum fetuin-B increased during successful IVF cycles (n = 15, P < 0.0001), but did not change in unsuccessful IVF cycles (n = 6, P = 0.118) despite increased estradiol levels (P = 0.0019 and P = 0.0254, respectively).

LIMITATIONS, REASONS FOR CAUTION

The female volunteers self-reported their respective hormone medication. Medication was verified by serum estradiol, LH and progesterone measurements. For oocyte harvesting, the vaginal wall was punctured once only to minimize co-morbidity. Low grade cross-contamination of individual follicular fluid aspirates and contamination of the follicular fluid with small amounts of blood were inevitable. Samples were routinely checked for the presence of hemoglobin that would suggest blood contamination. Only samples containing <250 erythrocyte equivalents/µl were used for analysis.

WIDER IMPLICATIONS OF THE FINDING

Serum fetuin-B may be used as a marker to predict the fertilization success in IVF. Fetuin-B levels attained during IVF stimulation may help to make an informed decision whether oocytes should be fertilized by IVF or by ICSI to overcome the zona pellucida as a barrier.

STUDY FUNDING/COMPETING INTERESTS

The research was supported by a grant from Deutsche Forschungsgemeinschaft and by the START program of the Medical Faculty of RWTH Aachen University. J.F., E.D., J.N., B.R. and W.J.-D. declare that they are named inventors on the RWTH Aachen University patent application EP 13157317.2, 'Use of fetuin-B for culture of oocytes', applied for by RWTH Aachen University.